Chitika, which runs Web-based ad network., said its findings are based on hundreds of millions of ad impressions from Dec. 1 to Dec. 27.

Chitika found that the iPad's share of tablet Web traffic declined by 7.1 percentage points -- from 86% to 78.9% -- after Christmas Day, 2012.

Kindle Fire had the largest share of the Android tablets, at 7.51%, up 3 percentage points since Christmas. The Samsung Galaxy tablets (7-in. And 10-in.) hold a 4.3% share, up 1.38 percentage points since Christmas, while the share of Web traffic on Google Nexus (7-in. and 10-in.) devices has doubled to 2% since Dec. 25.

Meanwhile, Apple's iPhone 5 maintains the largest share of smartphone Web traffic -- 8.27%. The iPhone is followed by the Samsung Galaxy S III smartphone, which holds a 4.29% share of Web traffic.